1. Technical Field
The present invention relates generally to a power management apparatus and a multi-source energy harvesting system using the apparatus and, more particularly, to an apparatus and system that store power in a battery by inputting the power from two or more energy harvesting sources (power sources).
2. Description of the Related Art
As the miniaturization of peripheral devices has become more and more important nowadays, the supply of power has become a serious problem due to limited battery lifetime of the peripheral devices. It is inefficient to periodically replace a battery or recharge the battery in a device that must be operated for a long period of time because high cost and much time are required.
Technology for solving this problem is energy harvesting. Energy harvesting is technology for harvesting ambient wasted energy such as light, heat or vibration, converting harvested energy into electric energy, and utilizing such electric energy. At the present time at which environment-friendly energy is emphasized, such energy harvesting is increasingly attracting attention. Accordingly, energy harvesting systems for converting energy from various energy sources such as photovoltaic or solar devices, piezoelectric devices, or thermal energy converters into electric energy and supplying electric power without being supplied with external power have been presented in various manners.
In order to improve the performance of power supply in an energy harvesting system, the management and distribution of power by the energy harvesting system must be favorably performed upon simultaneously utilizing two or more energy sources. That is, in the energy harvesting system, it is important to efficiently supply harvested powers, input from two or more harvesting sources either simultaneously or at different times, to a battery or an electric energy storage device (hereinafter collectively referred to as a “battery”) having the same function as the battery without wasting power.
Further, when an algorithm for a power management distribution circuit is implemented using a circuit, the complexity and power consumption thereof must be minimized.
As preceding technology related to this, there is technology which is published in the academic journal of Design, Automation & Test in Europe Conference & Exhibition in March, 2011 (entitled “An Effective Multi-Source Energy Harvester for Low Power Applications”) and which supplies power to a load depending on the charge and discharge conditions of a battery in an energy harvesting system having a plurality of harvester inputs.
The technology disclosed in the academic journal (“An Effective Multi-Source Energy Harvester for Low Power Applications”) is configured to select a harvester to be connected to a load using only a Schottky diode. In this case, since the Schottky diode is used, there is a high probability that power loss caused by the turning-on of the diode will occur.